1. Field of the Invention
This invention relates to production of principally hydrocarbon liquid and gaseous fuels from organic carbonaceous solids by countercurrent flow of heat-containing gas with free fall solids through a reactor, the solids passing sequentially through a solids preheat and pretreatment zone, a reaction zone, and a gas preheat zone. Liquid and gaseous fuels may be produced from organic carbonaceous materials such as oil shale, coal, peat and biomass.
2. Description of the Prior Art
The worldwide energy shortage has encouraged consideration and improvement of various processes for production of hydrocarbon fuels which do not involve petroleum products. Non-petroleum materials such as oil shale, coal, peat and biomass represent a large potential energy resource.
The production of hydrocarbon fuels by hydroconversion of oil shale is well known. For example, U.S. Pat. No. 4,003,821 teaches production of liquid hydrocarbons from oil shale by passing a hydrogen-rich gas stream countercurrent to a packed moving bed or fluidized bed of oil shale particles. The '821 patent teaches use of hydrogen sufficient to meet chemical requirements and the desirability of a sufficient excess of hydrogen to convert all of the hydrocarbons and carbon monoxide produced to methane. U.S. Pat. No. 3,922,215 teaches production of liquid hydrocarbons from oil shale by passing a hydrogen-rich gas stream in contact with oil shale particles in a moving bed. The '215 patent teaches the preferability of passing the hydrogen-rich gas stream in cocurrent relation with the oil shale particles to avoid condensation of hydroretorted liquids. The problems of condensation of liquids on the solid particles has been recognized by the prior art, for example, in U.S. Pat. No. 3,619,405. U.S. Pat. Nos. 3,891,403 and 3,929,615 teach production of high methane content gas from oil shale by hydrogasification.
Several patents teach various methods of retorting hydrocarbonaceous solids utilizing moving solids beds wherein gas passes countercurrently, such as U.S. Pat. Nos. 3,841,992; 3,619,405; 3,503,869; 2,899,365 and 3,297,562.
Free fall oil shale hydrogasification is taught by U.S. Pat. No. 3,421,868. The '868 patent teaches production of relatively high Btu gas from oil shale by passing freely falling oil shale in contact with hydrogen which is passed either cocurrent with or countercurrent to the free falling shale. The '868 patent teaches the desirability of low gas to shale ratios and flow rates of hydrogen gas much lower than flow rates of shale solids, resulting in much longer gas residence time than solids residence time within the reactor. The process of the '868 patent does not require heat input to the reaction zone. The '868 patent teaches that the disclosed free falling shale process substantially reduces decomposition of mineral carbonates while providing substantially the same gaseous yield as previous moving bed processes.
U.S. Pat. No. 4,012,311 teaches a process for high yield of coal tars by contacting coal in a series of free fall reaction zones with a cocurrent flow of hydrogen followed by quick quenching and removal of coal tar prior to entry to the next reaction zone. The '311 patent teaches low hydrogen to coal ratios and the importance of very rapid heat-up, short residence time, and quenching.